This invention relates to a laser-welded article that a laser-transmissible-absorptive molded workpiece including nigrosine alone as colorant and a laser-absorptive molded workpiece are welded by laser at a time and unified.
For mutually joining workpieces made from a synthetic thermoplastic resin material, a method for laser welding is known.
Such laser welding is executed for example as follows. As shown in FIG. 2, a laser-transmissible workpiece 11 is used for one workpiece and for the other workpiece, a laser-absorptive workpiece 12 is used. These workpieces are then put together. A laser 13 is irradiated from a side of the laser-transmissible workpiece 11 towards the laser-absorptive workpiece 12. And the laser 13 transmitted through the laser-transmissible workpiece 11 is absorbed into the laser-absorptive workpiece 12, and then heat is caused thereat. The heat melts the laser-absorptive workpiece 12 mainly at a laser-absorbing part, and then it melts the laser-transmissible workpiece 11 to weld both workpieces. After cooling, the laser-transmissible workpiece 11 and the laser-absorptive workpiece 12 are firmly joined at a welding position 14.
Merits of the laser welding are feasibility of welding workpieces without any contacts of a laser beam source to workpieces being due to weld; little thermal influence on laser-absorbing neighborhood by local heat; no threat of mechanical vibration; feasibility of mutually welding fine parts or workpieces having three-dimensionally complicated structures; excellent reproducibility; feasibility of maintaining sufficient airtightness; excellent welding strength; difficulty of recognizing a boundary line of a welding position by visual observation; no generation of dust and so on.
According to the laser welding, it is not only capable of welding certainly by simple operation but also achieving equal or more welding strength, as compared with prior methods for joining resin parts. Examples of the prior methods for joining resin parts are clamping by a clamp such as a bolt, a screw, a clip and so on, adhering by an adhesive material, vibration welding, ultrasonic welding and so on. The laser welding also achieves labor saving, improvement of productivity, lowering of production costs and so on because of its little vibratory or thermal influence on the laser-welded article. Accordingly, under an automobile industry, electric industry or electronic industry for example, the laser welding is practical for joining functional parts or electronic parts that are due to avoid the vibratory or thermal influence thereon. Also the laser welding can be adapted for joining resin parts having a complicated shape.
In Japanese Patent Provisional Publication No. 2004-148800, a method for the laser welding is mentioned. In the method, a first resin workpiece that has weak absorptiveness to a laser and a second resin workpiece that is absorptive to a laser are put together, and then a laser is irradiated from a side of the first resin workpiece to weld both workpieces. In this case, however, the first resin workpiece is prepared by kneading a resin and an additive such as a copolymer of ethylene and/or propylene and another olefin or vinyl compound. And the first resin workpiece includes relatively much additive. Therefore, there is a problem that the resin property of the first resin workpiece is easily influenced by the additive. Also, there are some other problems.
Depending on a sort of the resin and the additive, a separation of layers in the kneading procedure, a deterioration of strength of the welded article, and a restriction of using any resin are caused.